A core layer for reinforcing the rubber used to constitute a conveyor belt by bearing the tension generated at the time of stretching is embedded in a conveyor belt. Steel cords constituted by steel wires intertwined together are used as reinforcing members which constitute the core layer. The structures of steel cords vary, but there is a known strand structure which, for example, has a plurality of sheath strands intertwined around the outer circumferential surface of a core strand (specifically, see Japanese Unexamined Patent Application Publication No. 2012-036539). To manufacture a conveyor belt, a core layer composed of a plurality of steel cords extending side by side in parallel is embedded in an unvulcanized rubber member to form a molded article. Thereafter, the molded article is heated at a predetermined temperature and pressurized at a predetermined pressure in a vulcanization process to vulcanize the unvulcanized rubber. Thus, a conveyor belt in which a core layer composed of steel cords is embedded in the rubber is completed.
In recent years, there has been an increasing awareness of energy conservation, and the demand for energy conservation in conveyor belts has intensified as a result. For example, when a conveyor belt is reduced in weight, the energy required to transport and use the conveyor belt can be reduced. Alternatively, when a conveyor belt is reduced in thickness, this contributes to a reduction in weight and also enables a reduction in vulcanization time, which makes it possible to reduce the energy required for manufacture.
Therefore, reducing the weight and thickness of a core layer makes it possible to achieve energy conservation. However, when a core layer is simply reduced in weight and thickness, there is a problem in that the original reinforcing function of the core layer is diminished.